Compared to charge coupled device (CCD) sensors, a CMOS image sensor has many advantages such as low voltage operation, low power consumption, compatibility with logic circuitry, random access, and low cost. Among the CMOS image sensors, a phase detection auto-focus (PDAF) CMOS image sensor is widely used. The PDAF CMOS image sensor adapted photodiode in conjunction with metal grids disposed thereon to render phase detection, thereby achieving a focus function.
The current isolation method for adjacent photodiodes is mostly implant isolation. However, implant isolation is not sufficient to eliminate the cross-talk effect between adjacent photodiodes, and the sensitivity of the PDAF CMOS image sensor is compromised.